In the USA, the term Party Wall refers to the wall within a condominium or townhome complex that separates two neighboring units. It is also known as a parti-wall, parting wall or common wall.
Party walls can be non-structural, but laws in various jurisdictions outline requirements for how party walls must be constructed. Rights and obligations are also governed by state statutes and common law.
Party walls are sometimes built with added insulation, so sound is minimized from adjoining units. Some building codes require them to be built as a fire wall using noncombustible material from the foundation to the roof. Fire walls help slow the spread of the fire into adjoining units, making it safer for tenants and limiting property damage.
Some builders use concrete to separate the spaces, floors and ceilings. Much of the newer construction relies on air to fill the walls between units.
There are formal laws about sharing common walls in many countries. For example, in 1996 Britain created the official Party Wall Act. As a formal part of British law, surveyors settle party wall disputes. The act specifies exactly what owners or tenants may and may not do to their side of a shared wall. Painting, decorating, and adding shelves to party walls is permitted. Major construction or changes to the structural components without an agreement from the other party is not allowed.